I think they’re saying that both sun and earth magnetic fields would tend to shunt incoming heavy nuclei aka cosmic rays away from the earth. But in what experimental vessel did anybody ever verify this basic assertion about cosmic rays and clouds?
Look up “Svensmark” and “cosmic rays”. Dr. Svensmark has done major work over the last two decades on this effect, and has done some experimental work. He’s now leading a team creating a huge experimental chamber at CERN to study it further.
Still some years away from full understanding, but it is critical work. The IPCC recognizes that clouds are among the least understood factors affecting the Earth’s climate, and though they don’t ever delineate this: it would take only on the order of a 1% change of cloud cover to account for ALL the warming we’ve seen in the 20th century.